In general, metropolitan and wide area communication networks are often used for interconnecting Local Area Networks (LANs). In previous implementations, metropolitan and wide area communication networks were often based upon technologies such as Asynchronous Transfer Mode (ATM), Synchronous Optical Network (SONET), and Frame Relay (FR) technologies, which were optimized for voice communications services. With the increased use of the Internet as a communications medium, non-voice traffic (typically referred to as data traffic) is becoming the most prevalent type of network traffic. In order to meet the increasing demand for data communications services in metropolitan and wide areas, many newer metropolitan and wide area communication networks utilize Ethernet, at Layer 2 of the Open System Interconnection (OSI) model, to connect nodes within the network. Ethernet is a popular Layer 2 protocol for use in such networks, primarily due to its compatibility with the installed base of end users, its compatibility with Internet Protocol (IP), its overall flexibility, and its cost (e.g., it is relatively cheap to deploy as compared to other Layer 2 technologies such as ATM, SONET, and FR).
While the use of Ethernet as the Layer 2 technology in metropolitan and wide area communication networks has many advantages as described above, use of Ethernet as the Layer 2 technology in metropolitan and wide area communication networks has disadvantages. For example, end user customers, such as businesses, that are targeted to utilize metropolitan and wide area communication networks often desire advanced network services, such as quality of service (QoS) guarantees, permanent virtual circuits (PVCs), Virtual Leased Lines (VLLs), transparent LAN services (TLS), and the like. While many of these advanced services can be provided by a network that utilizes a Layer 2 technology such as ATM, SONET, or FR, Ethernet, on the other hand, was not originally designed to provide advanced services and, as a result, solutions to customer needs can be more difficult to implement in Ethernet-based networks.
One Ethernet technology that is presently utilized in many metropolitan and wide area communication networks to provide advanced services to customers is Virtual LAN (VLAN) technology. A VLAN is a group of network devices on different physical LAN segments that can communicate with each other as if they are on the same physical LAN segment. In general, network devices, and the respective network traffic of those network devices, can be mapped into VLAN groups using various types of VLAN mappings, e.g., port-based VLAN mapping, Media Access Control (MAC) address-based VLAN mapping, protocol-based VLAN mapping, IP subnet-based VLAN mapping, application-based VLAN mapping, and explicit VLAN tagging, and the like, as well as combinations thereof.
A widely accepted standard for implementing explicit VLAN tagging within an Ethernet network is defined by in the Institute of Electrical and Electronics Engineers (IEEE) 802.1Q standard. In general, implementation of 802.1Q VLANs involves tagging packets with a Tag Control Information field that identifies the VLAN to which the packets belong. According to the IEEE 802.1Q standard, the Tag Control Information field includes a 12-bit VLAN Identifier (VID) field that enables VLANs to be uniquely identified. In addition to the IEEE 802.1Q standard, the IEEE 802.1ad standard (denoted as the Provider Bridge specification) defines an approach, often referred to as Q-in-Q, in which VLAN tags may be “stacked” to allow not only separation of customer traffic, but differential treatment of customer traffic within the service provider network.
In addition to the above-described Ethernet technologies, Provider Backbone Bridging (PBB), as defined in the IEEE 802.1ah standard, is an Ethernet-based technology that enables layering of the underlying network into customer and provider domains with isolation between customer MAC addresses and provider MAC addresses. In general, the IEEE 802.1ah standard defines an approach of encapsulating customer Ethernet frames using a service provider header that includes a backbone source address (B-SA), a backbone destination address (B-DA), a backbone VLAN ID (B-VID), and a service instance ID (I-SID). As a result, the IEEE 802.1ah standard allows for “MAC tunneling” encapsulation and bridging of frames across a PBB network.
Disadvantageously, however, customer QoS indicators enabled by standards such as the IEEE 802.1Q standard and the IEEE 802.1ad standard cannot currently be transported across PBB networks.